In a typical wireless communication system, User Equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks (CNs).
A user equipment is a mobile terminal by which a subscriber can access services offered by an operator's core network. The user equipments may be for example communication devices such as mobile telephones, cellular telephones, or laptops with wireless capability. The user equipments may be portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station or a server.
User equipments are enabled to communicate wirelessly in the wireless communication system. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between the user equipment and a server via the radio access network and possibly one or more core networks, comprised within the wireless communication system.
The wireless communication system covers a geographical area which is divided into cell areas. Each cell area is served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also on cell size.
A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some radio access networks, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to one or more core networks.
UMTS is a third generation, 3G, mobile communication system, which evolved from the second generation, 2G, mobile communication system GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to further evolve the UTRAN and GSM based radio access network technologies.
In the context of this disclosure, a base station as described above will be referred to as a base station or a Radio Base Station (RBS). A user equipment as described above, will in this disclosure be referred to as a user equipment or a UE.
The expression DownLink (DL) will be used for the transmission path from the base station to the user equipment. The expression UpLink (UL) will be used for the transmission path in the opposite direction i.e. from the user equipment to the base station.
A wireless communication system typically consists of a large number of cells. The radio communication in a cell may suffer from poor transmission quality due to interference in the radio environment. The interference source may be for example other cells or user equipments, or other, external, sources.
Several important factors for obtaining a required balance between area coverage, system capacity and user satisfaction in a wireless communication system may be related to transmission parameters, such as for example antenna tilt, antenna direction, antenna gain and transmitter output power. Some such parameters, for example receiver sensitivity, coding and modulation may be fixed or limited to certain values in the standards.
Determining a suitable transmission parameter value such as an antenna tilt et cetera is far from a trivial task, since the settings in one cell may not only impact the situation in the cell, but also heavily impact the situation and transmission quality in other cells.
Computer simulations may be used to evaluate transmission parameters such as antenna tilts et cetera, and their impact on the radio situation and transmission quality for several cells. A drawback with this is, however, that the results cannot be more accurate than the input into the simulations. Hence, the simulation may not be valid if reality differs from the simulation, or changes over time.
For example, if user equipments in reality are located differently and moves in different ways compared to a simulated scenario, the result of the simulation may not be valid for the real situation. Moreover, changes in the real environment, such as new houses, new highways et cetera, may not be updated in the simulated scenario, which may also render a simulation result invalid. Such changes in the environment does not only change the actual geography, but also the distributions and behaviors of subscribers, and thus of user the equipments. This in turn affects the traffic patterns and the interference in the radio environment.